1. Field of the Invention
This invention relates to exercise equipment and machines for home commercial use.
2. Description of the Related Art
For example, commonly owned U.S. Pat. No. 5,106,081 to Webb discloses a leg press machine that incorporates a four bar linkage configuration for changing the angle of inclination of the foot plate to maintain a normal orientation to the lower legs of a user throughout the movement of the leg press exercise. While providing an instantaneous axis of rotation for the foot plate, the linkage between the four bar linkage of the leg press and the weight stack used as a resistance force, although quite functional, is also quite cumbersome. The Webb machine includes, inter alia, a shaft between a sprocket on one end as part of the weight stack and variable radius cam on the other end connected to the four bar linkage.
Further, the force curve of the exercise machine disclosed in Webb is fairly constant (as shown by the before and after positions of the four bar linkage and the attached chain and sprocket) throughout the exercise motion. A flat force curve does not provide the most effective exercise results for a user because of the elementary principles of momentum—a body in motion tends to stay in motion, while a body at rest tends to stay at rest. Therefore, it may be more difficult for a user to start the exercise and put the mass (resistance force) in motion. However, once in motion, the exercise will be easier for the user because of the momentum already imparted to the user. Thus, if a leg press exercise machine were designed with an increasing force curve through the pressing motion of the exercise, a user would get a better workout. The exercise would be easier to start, but the resistance would increase throughout the press motion, thereby making the user's muscles work harder than if the force curve were flat.